$\dfrac{1}{3} - \dfrac{6}{5} = {?}$
Answer: $ = {\dfrac{1 \times 5}{3 \times 5}} - {\dfrac{6 \times 3}{5 \times 3}} $ $ = {\dfrac{5}{15}} - {\dfrac{18}{15}} $ $ = \dfrac{{5} - {18}}{15} $ $ = -\dfrac{13}{15}$